DESCRIPTION (applicant's abstract): Recent widely-accepted advances in electrochemical biosensor technology will be combined with the unique silicon microfabrication technology developed in our laboratory to produce low cost single-use disposable (consumable) devices for painless physiological measurements on a blood sample volume of 200 nanoliters. The silicon devices consist of a microneedle comparable in cross-section to a human hair integrated with a cuvette containing a miniaturized biosensor. In use, the blood sample is drawn into the cuvette through the silicon microneedle from the microvasaculature of the skin. Enzyme activities in blood can be measured in these devices by depositing a substrate to the target enzyme in the cuvette and employing an integrated biosensor specific to this substrate to monitor the rate of decrease in its concentration as reaction occurs due to enzyme in the blood sample. The example enzyme chosen for the work of Phase I was cholinesterase. The combination of a biosensor with a silicon consumable to provide a practical technique for monitoring enzymatic activity in blood is not restricted to cholinesterase, but is an enabling technology applicable to many other enzymes. The resultant sampling and assay system will require a much lower sample volume than current methods, provide a faster response, and be easy to use by personnel without special training in chemical analysis. PROPOSED COMMERCIAL APPLICATION: Markets include quality control in the flood industries, emergency medicine, control of blood levels of therapeutic drugs, and physiological monitoring of many analytes and enzyme activities for clinical and research purposes.